Purification of normal cellular prion protein from human platelets and the formation of a high molecular weight prion protein complex following platelet activation

A method for the extraction and purification of PrP C, in its native monomeric form, from outdated human platelet concentrates is described. Both calcium ionophore platelet activation and lysis in Triton X-100 were evaluated as methods for the extraction of soluble platelet PrP C in its monomeric form. Following platelet activation, the majority of released PrP C was detected as a disulphide linked high molecular weight complex, which under reducing conditions could be separated into what appear to be stable non-disulphide linked PrP dimers or PrP covalently linked to another as yet unidentified protein. This phenomenon appears to be unique to activation since only monomeric PrP C was detected following lysis of resting platelets. Subsequently, PrP C was purified from the Triton X-100 lysate by sequential cation ion exchange and Cu 2+ affinity chromatography. From 10 L of outdated platelet concentrate, we were able to recover 1.29 mg PrP C at a purity of 92%.